1. Field of the Invention
The invention concerns an industrial truck with a lifting stand that is swivellable around a tilting axis located outside of the wheel base in a lifting stand bearing support, at least in certain operating states, and with a monitoring device for detecting and indicating the loading state.
2. Description of the Art
Industrial trucks with a tilting axis of the lifting stand outside of the wheel base are, for example, the ordinary counterweight fork lift trucks, in which the lifting stand tilting axis is located in the front area of the vehicle crosswise to the longitudinal axis of the vehicle. In addition, the so called side fork lift trucks take up the load outside of the wheel base with a lifting stand displaceable crosswise to the direction of movement. The load is transported after the lifting stand is again drawn back completely. Fork lift reach trucks also have a displaceable lifting stand for receiving the load outside of the wheel base. For a better understanding, the following statements refer to counterweight fork lifts, but are not limited to them.
Because the load to be transported is taken up outside of the wheel base, a torque develops around the front axle in counter-weight fork lifts. A torque acting in the opposite direction is imposed by the weight of the fork lift truck itself. The torque deriving from the load is dependent on the weight of the load and on the distance of the load center from the tipping axis (front axle), which is also modified in the case of a tilting movement of the lifting stand. When an excessively large load is taken up or if the distance of the load center from the tipping axis is too great, there is the danger that the tipping limit of the fork lift is exceeded. Even if the tipping limit is not reached in the static state, the fork lift truck can tip over due to dynamic forces in the moving vehicle, e.g., centrifugal forces in rounding curves or inertial forces during braking and acceleration. There have been many attempts to prevent this or at least signal the driver in good time so that the latter can take countermeasures.
It is thus known from the DE-OS 32 03 553 to detect the loading state of the fork lift truck from the pressure in the lifting cylinder and the pressure in the tilting cylinder of the lifting stand. The loading state is displayed graphically on an indicating field within view of the driver. If there is the danger of the fork lift truck tipping due to an unfavorable load state, this is also signalled. Detection of the loading state via the hydraulic pressure has the shortcoming that due to the fastening of the lifting cylinder on the lifting stand and the resulting position change in the cylinder in the case of a tilting movement of the lifting stand, a force is measured that does not correspond in all cases to the actual weight force, but only to a force component in the acting direction of the lifting cylinder axis, which can lead to imprecision.
The present invention proposes to offer a fork lift truck of the above type, in which the danger of tipping is further reduced through an improved monitoring of the loading state.